1. Field of the Invention
The present invention relates to a system for driving a turbocharger installed in an internal combustion engine mounted on a motor vehicle such as an automobile, and more particularly to a drive system for a turbocharger combined with a rotary electric machine which can operate as an electric motor depending on operating conditions of the internal combustion engine.
2. Description of the Prior Art
Turbochargers which are now in widespread use have a compressor mounted on the shaft of a turbine that is driven by the energy of exhaust gases emitted from an engine. The compressor compresses intake air to supercharge the engine for increasing the output power of the engine. Various proposals have been made to install a motor/generator on the rotatable shaft of the turbocharger and control the motor/generator depending on operating conditions of the engine.
The applicant has proposed, as one of such proposals, a turbocharger for use with an internal combustion engine, the turbocharger being combined with a motor/generator. When the engine operates at a low speed under a high load, electric power is supplied to the motor/generator to operate the motor/generator as a motor to assist the turbocharger in supercharging the engine (see Japanese Laid-Open Patent Publication No. 60-195329).
According to the proposed turbocharger, the electric power is supplied from a battery to the motor/generator for assisting the turbocharger in supercharging the engine. When the motor vehicle runs up a long uphill road, the electric power stored in the battery is greatly reduced or used up, and the battery can no longer be used as an electric power supply on the motor vehicle.